In the following section, we will exploit this interpretation in order to define general equivariant convolution operators.
But first, we will consider the PFN from this perspective.
The PFN as defined in [1]} is given by
\(\mathrm {PFN}(S) = F\left( \sum _k \Phi (\vec{x}_k, q_k) \right) \,.\) 
